TFT LCD panels are often employed in portable consumer-electronics devices, such as smartphones, as displays. To save battery power, these devices are usually programmed to turn off the panels when the users are not using the devices. However, it is observed that when a TFT LCD panel resumes displaying an image from a display-off mode, the resumed picture displayed on the panel may flicker. The occurrence of flickering is especially noticeable if the panel has been stayed in the display-off mode for a long time. The occurrence of flickering is negative to user experience. Furthermore, many portable consumer-electronics devices are equipped with a “knock-on” feature. By the knock-on feature, a portable device originally having its touch-sensing-enabled LCD panel turned off for saving power is waken up to resume image display when a user knocks on the panel. The noticeable flicker is highly undesirable to positive user experience when the knock-on feature is used. There is a need in the art for a technique to avoid or minimize flickering when the TFT LCD panel resumes image displaying from the display-off mode.